The present invention generally relates to optical communications and, more particularly, to systems and methods for splicing optical fibers.
A fiber optic splice is a permanent fiber joint for establishing an optical connection between two optical fibers. Certain system designs require that optical connections exhibit specific optical properties, e.g., low loss, that are met only by fiber optic splices. Fiber optic splices also permit repair of optical fibers that are damaged during installation, for example.
To form a fiber optic splice, the optical fibers being spliced are actively and/or passively aligned. Active alignment typically includes monitoring the signal loss of an optical signal propagating from one optical fiber, through the splice, and to the other optical fiber. By monitoring the signal loss, the optical fibers can be accurately aligned, i.e., when signal loss is minimized, proper alignment is achieved. Although active alignment procedures are capable of producing low-loss fiber optic splices, these procedures generally are considered time-consuming and expensive, as they typically require the use of a power meter or optical time-domain reflector.
In another active alignment procedure, precision reference surfaces are used to align the optical fibers during splicing. For example, U.S. Pat. No. 3,928,102 to Rowe et al., which is incorporated herein by reference, discloses a method for joining two optical fibers in which both are held parallel to a reference surface by surface tension of a liquid. In particular, the liquid is spread on a work table upon which the fibers are placed. The optical fibers are held against the work table by surface tension of the liquid along the lengths of the optical fibers. Alignment is achieved by transmitting light along one fiber and rotating the other until the intensity of the light received attains a maximum. The optical fibers then are joined at their ends by the application of an adhesive or heat. Clearly, this technique requires the use of a reference surface and can be messy.
Based on the foregoing, there is a need for improved systems and methods that address these and/or other perceived shortcomings of the prior art. For example, what is needed is a method for splicing optical fibers that is less expensive and time-consuming than those incorporating active alignment.
The invention involves passive alignment of optical fibers by using surface tension of an adhesive applied at the ends of the fibers. Typically, at least one of the fibers includes a surface, proximate to an end of the fiber, that exhibits low wettability with respect to the adhesive. When the adhesive is applied to the end of the fiber, the adhesive tends to locate itself at the end surface, i.e., the adhesive does not spread out along the adjacent side surface of the fiber. Therefore, when the end of the other fiber contacts the adhesive, surface tension of the adhesive passively aligns the fibers. Since the adhesive is optically transparent, light can propagate from one fiber to the other via the adhesive. In some embodiments, a cladding material can be applied to the adhesive to form a cladded optical waveguide between the fibers.
A representative embodiment of an optical system in accordance with the invention includes first and second optical fibers, each of which has an end surface and a side surface adjacent to the end surface. An adhesive joins the end surface of the first optical fiber to the end surface of the second optical fiber. Additionally, at least a portion of the end surface of the first optical fiber exhibits a wettability for the adhesive that is higher than a wettability for the adhesive exhibited by at least a portion of the side surface of the first optical fiber.
Methods for splicing a pair of optical fibers also are provided. One such method includes: providing first and second optical fibers, each of which has an end surface; applying adhesive to the end surface of the first optical fiber; positioning the first and second optical fibers so that the adhesive extends between the end surface of the first optical fiber and the end surface of the second optical fiber; and aligning the first and second optical fibers using surface tension of the adhesive.
Clearly, some embodiments of the invention may address shortcomings of the prior art in addition to, or in lieu of, those described here. Additionally, other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.